This return is no longer necessary since essentially someone calling this just cares if it raises an exception or not.

I'm not sure how much I like the name `conforms` for this anymore. `conforms` sounds like it should return a `bool`. That's why I suggested `check` do this, and leave `conforms` to return a bool if `check` raised a `FormatError` (even though in our code we'd never need to use `conforms` anymore).